Process for crimping threads of fiber-forming polyolefins



Nov. 14, 1967 H. HYER ET AL PROCESS FOR CRIMPING THREADS OF FIBER-FORMING POLYOLEFINS I Filed March 2, 1964 IN VEN T028 H6018 Hfiyer Egi data 6 [jars He llnz [(bp he BY fl M56 ATTDJENE Y3 United States Patent Ofiice 3,352,959 PROCESS FOR CRIMPIN G THREADS OF FIBER-FORMING POLYOLEFINS Hans Hoyer, Frankfurt am Main, Egidius Welfers, Niederhofheim, and Heinz Kiipke, Sulzbach, Germany, assignors to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany Filed Mar. 2, 1964, Ser. No. 348,519 Claims priority, application Germany, Mar. 5, 1963, F 39,172 4 Claims. (Cl. 264-282) The present invention relates to an improved process for imparting a permanent crimp to yarns or threads of fiber-forming polyolefins.

It is known that synthetic yarns or threads can be crimped by withdrawing the thread from a feed roll and conducting it over a thread-guide and through a pair of conveyor rollers, which is to prevent the thread from untwisting, whereupon the thread is' passed through a heating device at the end of which is fitted a so-called rotating tubule through which the thread to be crimped is conducted. From this rotating tubule the thread is passed through a second pair of conveyor rollers to the winding roller. The speed of the thread, the number or rotations of the rotating tubule as well as the tension of the thread and the temperature of the heating device can be varied to a large extent. By an appropriate choice of the aforementioned working conditions, the type and the durability of the crimp is influenced to a large extent. The thread is twisted and untwisted between the two roller pairs so that it issues from the lower conveyor rollers with the same torsion with which it was fed to the upper conveyor rollers. The twist temporarily im parted to the thread by the rotating tubule is fixed by the heat effect of the heating device.

This crimping process which has been known hitherto bythe name of false twist process has proved to be very suitable for threadsof fiber-forming polyamides and linear aromatic polyesters. However, in the case of threads of fiber-forming polyolefins, especially polypropylene, a usefiul crimp was not obtained. Immediately on issuing from the lower conveyor rollers such threads exhibit a low degree of crimping which, however, disappears again when the threads are wound on the winding roller and which, even after several hours residence time of the thread on the winding roller, does not appear again when the thread is relaxed.

Now we have found that also threads of polyolefin, especially propylene, can be crimped in an entirely satisfactory manner when crimping is carried out in the same manner as in the case of the well-known false twist process, with the dilference, however, that the threads issuing from the second pair of conveyor rollers are cooled ofi? to a temperature within the range of from 20 to 60 C. and, moreover, allowed to shrink by at least 20 to 40% befiore being zfed to the winding roller.

A shrinkage of the threads can especially be obtained by carefully shoving the threads which are still warm on issuing from the heating device. Such a shoving is obtained when the threads, immediately after having issued from the lower conveyor rollers, are passed in one working operation through a suction device, the threads being sucked into said suction device by means of a pressure of 200 to 400 mm. of mercury. The re- 3,352,959 Patented Nov. 14, 1967 quired cooling of the threads is achieved by this measure; the threads are allowed to shrink to a considerable extent and, furthermore, they are shoved in a small degree.

The polyolefin threads treated by the novel process exhibit an intensive crimp and, above all, a good elastic behavior. A special modification of the process according to the invention consists in laying the threads, after they have issued from the suction device, on a belt conveyor from where they are tied to the winding roller.

The present invention also provides an apparatus for carrying out the novel process. This apparatus is described with reference to the accompanying drawing by way of example only in which (1) is a feed roll, (2) a pair of conveyor rollers, (3) is a heating device, (4) a rotating tubule, (5) a second pair of conveyor rollers, (6) a suction device and (7) a winding roller.

The following example serves to illustrate the invention, but it is not intended to limit it thereto:

Example An untwisted thread of fiber-forming polypropylene having a titer of deniers and 24 individual filaments, which had been drawn in a ratio of 1:3.6 and which had not been subjected to a heat treatment, was crimped in the manner described above. The thread issuing from the pair of conveyor rollers at the rate of 45 meters/ minute was drawn off by means of a suction device, in which a pressure of 300 mm. of mercury had been established, and wound in an entirely relaxed condition on a winding roller. By means of the suction device, in which reduced pressure was reigning, the thread was simultaneously cooled to 25 C., allowed to shrink by 30% and shoved. The polypropylene thread treated in this manner had an excellent permanent crimp.

We claim:

1. In a process for crimping thread of fiber-forming polyolefins in which said thread passes in the following order through a first set of conveyor rollers, a heating device, a rotating twist tubule, a second set of conveyor rollers and a winding roller, the improvement which comprises applying subatm ospheric pressure to said thread between said second set of conveyor rollers and said winding roller for cooling said thread to temperatures ranging from 20 to 60 C. and shoving it toward said winding roller and rotating said winding roller slowly enough to wind said thread upon it in a relaxed condition free of tension whereby it is shrunk about 20% to 40% before being Wound upon said winding roller.

2. A process for crimping threads as claimed in claim 1, wherein thread of polypropylene is used.

3. A process for crimping threads as claimed in claim 1, wherein the thread is laid on a belt conveyor prior to being wound on a roller.

4. An apparatus for crimping thread of fiber-forming polyolefins comprising a first set of conveyor rollers, a heating device, a rotating twist tubule, a second set of conveyor rollers and a winding roller, means for applying subatmospheric pressure to said threads disposed between said seoond set of conveyor rollers and said winding roller for cooling said thread to temperatures ranging from 20 to 60 C. and shoving it toward said winding roller and rotating means connected to said winding roller (for notating said winding roller slowly enough to wind said thread upon it in a relatxed condition free of ten- 3 sion whereby it is shrunk about 20% to 40% before being Wound upon said Winding roller.

References Cited UNITED STATES PATENTS 2,668,430 2/1954 Laros 281 2,890,568 6/1959 Willens 2872 2,951,330 9/1960 Bouvet 28-72 4 2,975,474 3/1961 Smith 264282 3,016,678 1/ 1962 Nesbitt-Dufort 2872 3,022,565 2/1962 Fitzgerald 571 57 FOREIGN PATENTS 1,383,663 11/1964 France.

ROBERT F. WHITE, Primary Examiner.

R. R. KUCIA, Assistant Examiner. 

1. IN A PROCESS FOR CRIMPING THREAD OF FIBER-FORMING POLYOLEFINS IN WHICH SAID THREAD PASSES IN THE FOLLOWING ORDER THROUGH A FIRST SET OF CONVEYOR ROLLERS, A HEATING DEVICE, A ROTATING TWIST TUBULE, A SECOND SET OF CONVEYOR ROLLERS AND A WINDING ROLLER, THE IMPROVEMENT WHICH COMPRISES APPLYING SUBATMOSPHERE PRESSURE TO SAID THREAD BETWEEN SAID SECOND SET OF CONVEYOR ROLLERS AND SAID WINDING ROLLER FOR COOLING SAID THREAD TO TEMPERATURES RANGING FROM 20* TO 60*C. AND SHOVING IT TOWARD SAID WINDING ROLLER AND ROTATING SAID WINDING ROLLER SLOWLY ENOUGH TO WIND SAID THREAD UPON IT IN A RELAXED CONDITION FREE OF TENSION WHEREBY IT IS SHRUNK ABOUT 20% TO 40% BEFORE BEING WOUND UPON SAID WINDING ROLLER. 